Steam generating unit



Aug. 24, 1965 s. A. REHM 3,202,137

STEAM GENERATING UNIT Filed March 5, 1963 4 Sheets-Sheet 1 I I I I I l INVENTOR Gustav A. Rehm L020 8. Barry Attorneys Aug. 24, 1965 G. A. REHM STEAM GENERATING UNIT 4 Sheets-Sheet 2 Filed March 5, 1963 0 O O O O O o O O O O O O N 0 n mm m INVENTOR Gustav A. Rehml L020 8 Barry oouoooo Attorneys Aug. 24, 1965 G. A. REHM STEAM GENERATING UNIT 4 Sheets-Sheet 3 Filed March 5, 1963 Umn INVENTOR.

Gustav A. Rehm L020 8 Bonry Attorneys Aug. 24, 1965 G. A. REHM 3,202,137

STEAM GENERATING UNIT Filed March 5, 1963 4 Sheets-Sheet 4 N KO FIG.5

INVENTOR.

Gusiov A. Rehm L020 8: Barry Attorneys United States Patent 3,202,137 STEAM GENERATING UNIT Gustav A. Rehm, Milwaukee, Wis, assignor to Cleaver-Brooks Company Filed Mar. 5, 1963, Ser. No. 262,923 7 Claims. (Cl. 122-473) This invention relates to steam generating units of the package type and more particularly to improved combustion product and water circulation flow paths in such units.

The demand for a package type steam generating unit has increased steadily since their introduction into the market because of the simplicity of installing such units with the consequent savings in cost and time. The physical size of such units is somewhat limited to the means or mode of transporting the unit, and as .a result increased steam capacity must be obtained through more eflicient systems for transferring heat from the combustion products to the water in the boiler. The principal object of this invention is to provide a paclcage steam generating unit which accomplishes this result.

Another object is to provide a steam generating unit having a greater heat transfer capacity through more ellicient flow paths for the combustion products.

Another object is to provide an improved water circulation system for a package steam generating unit that takes advantage of the principles of natural water circulation and at the same time maintains a proper balance of the water in the system.

Another object is to provide a package steam generatmg unit that is readily accessible for maintenance and repair purposes.

Still another object of the present invention is to provlde a package steam generating unit having an improved water wall arrangement which protects the interior surfaces of the unit from the effects of radiant heat.

A further object of the invention is to provide an improved superheater structure for a package steam generating unit.

Another object is to provide'an improvedsuperheater structure having a substantially fiat steam temperature curve.

A still further object is to provide an improved structural arrangement for the convection tubes which simplities replacement problems.

Other objects and advantages will become readily apparent from the specification when read in conjunction with the drawings, in which:

FIG. 1 is a side View of the steam generating unit showmg" the position of the superheater at the end of the secondary furnace space and the bellies inthe convection tube space.

FIG. 2 is .a plane section of the steam generating unit in section showing the primary and secondary furnace spaces, the convection tube space and the position of the superheater.

FIG. 3 is a split sectional view taken on line 3-3 of FIG. 2 showing a cross section of the primary furnace space and the burner wall (front wall) water wall tubes.

j (FIG. 4 is a split sectional view takenon line 44 of FIG. 2 showing a cross section of the secondary furnace on the left hand side with the convection tubes and screen tubes on the right hand side and the superheater tubes as they are placed at the rear of the secondary furnace on the left side. p p FIG. 5 is an orthographic projection of the steam generating unit partly brolren away to show the arrangement of the interior of the boiler.

"Referring more specifically to the drawings, apa'ckage type steam generating unit is shown having a housing in- 'ice cluding a front wall .10 and a back or rear wall 12 closed on each side by suitable side walls 14 and 16. The floor level indicated at 18 is supported by any suitable base frame 20 set on foundations 21. The top of the boiler is closed by any suitable roof configuration as shown at 22. The housing is divided into a primary furnace space 24 and a combustion products space 26 by a pair of vertical walls 2-8 that project transversely from the side walls toward the center of the housing te-rminatin'gat 30 leaving an opening 31 therebetween. The various walls can be made of any suitable refractory and/ or insulating material, the details of which are well known in the art. The front wall of the housing is provided with twin apertures 36 for mounting liquid or gaseous fuel burners. Other type of burners and sources of combustion products can be used in a unit of this type as described more fully hereinafter.

The boiler unit includes an upper drum 32 positioned in the upper central portion of the roof of the housing and a pair of lower drums 34a and 34b mounted in the floor on either side of the housing. The upper drum has the usual connections for outlet safety valves and feed valves and other conventional equipment which is unun portant to the present invention, The upper drum is directly connected to the lower drum by water wall tubes .37 in the front wall, water wall tubes 38 in the side walls and water wall tubes 39 in the vertical walls, which completely enclose the primary furnace space 24 with the exception of opening 31 to the secondary combustion products space. Two rows of water wall tubes 40 extend longitudinally from the termination 30 of walls 28 toward the rear Wall terminating at 41 and dividing the secondary combustion products space into a central longitudinal secondary furnace space 42 and reverse flow convection tube spaces 43.

Combustion products are supplied to the primary furnace space substantially completely burned out and then directed to the secondary furnace space 42 between the two rows of water wall tubes 40. The flow of combustion products from the primary furnace space around the ends 30 of walls 28 creates areas of turbulence at 44 as the combustion products flow into the secondary furnace space 42. The areas of turbulence insure the complete mixing of the combustion products and as a result the complete burning of any unburned combustion products as they flow through the secondary furnace space 42.

Referring momentarily to FIG. 3 of the drawings, the arrangement for water wall tubes 38 is shown for the top and bottom of the furnace space. Tubes 38a extend from drum 34b across the bottom of the primary furnace space and vertically upward into upper drum 32. These tubes are spaced a tube width apart to provide room for tubes 38c which connect drum 34a with the upper drum.

These tubes extend vertically upwardon the same side' of the housing as tubes 38a and are alternately arranged therewith but are bent to pass under the upper water drum and are turned back at their endsfor connection with the upper drum. Tubes 38d and 38b are similarly arranged Convection tubes 46 .are connected between the upper drum and lower drum in the spaces between the rows of water wall tubes 44), the vertical walls 28 and the side walls. These tubes extend from the rear wall forward to wall 28 and are arranged in pairs with a tube width space 77 being provided between each pair of tubes. Bafile 43 is positioned in this space parallel to wall 28 to isolate .a section of the convection tubes which will then act as .do'wncomer tubes as described hereinafter. Bafiles 50, 52, and 54 are positioned in the convection tube spaces to deflect the combustion products up and down across the convection tubes as they pass toward and out chimney outlets 56. The convection tubes may extend across the entire rear Wall of the boiler or be omitted from the space between walls to leave a superheater space 58 as seen in FIG. 2.

v The convection tubes are arranged in pairs with a space 77 slightly wider than the outside diameter of the tubes provided between each pair of tubes. The tubes can then be removed from the boiler and replaced by a new tube without disturbing any other convection tubes. Another important maintenance feature of this unit is the elimination of all headers and key caps in the boiler system. All of the water tubes are connected directly from drum to drum with unrestricted water and steam flow areas from drum to drum.

In the drawings, superheater 60 is shown positioned within space 58 so that the hot combustion products flowing through the central flow path will enter this space and be divided and turned through 90 to approximately 180 in the superheater as they enter the convection spaces 43. The superheater includes an inlet header 62 and an outlet header 64 both positioned on the rear wall of the housing. The inlet header is connected by pipe 65 to the steam outlet 66 in the upper drum. Both headers are accessible from the outside of the boiler for maintenance and repair. Superheater tube elements 66' are connected at right angles to the inlet and outlet headers and extend longitudinally into the secondary furnace space in parallel planes. Each superheater tube element is made up of one or more tubes 68, 70 (two tubes shown) bent in similar zig-zag fashion with one of the tubes located immediately behind the other tube and both tubes lying in a common plane. Each alternate tube element is staggered from the adjacent tube element (FIG. 2) in order to allow for the free flow of combustion products between the tubes in the tube elements. A number of screen tubes 72 are provided across the front of the superheater to reduce the temperature of the combustion products before they enter the superheater. The screen tubes are spaced from each other a suitable distance to allow for the free how of combustion products into the superheater space. Screen tubes 72 are not always required.

In large installations where the combustion products enter the secondary furnace space at an extremely high temperature, a row of water wall tubes 73 are positioned in the secondary furnace space parallel to water wall tubes 40. These tubes will reduce the temperature of the combustion products so that they will not burn in the superheater. A drain valve 75 is provided in the lower header 64 in order to completely drain the superheater whenever it is required.

This type of superheater provides a number of advantages over other types of superheaters presently being used. The multi row of tubes in each element provides a greater amount of surface area for the amount of space available for heat transfer. The staggered positioning of the superheater tube elements enlarges the spacing between adjacent tubes to allow for the free flow of combustion products through the superheater. One other important consideration is the location of the superheater at the end of the central flow path where the direction of gas flow changes. All surfaces of the superheater tubes are thereby subjected to the flow of combustion products thus increasing the amount of convection heat transfer. Also, each superheater tube is exposed to the same gas temperature, thus assuring uniform superheater tube metal and steam temperatures. Finally, it can be seen that the surface area of the superheater exposed to radiant heat from the secondary combustion space is related to the surface area of the tube elements exposed to convection heat transfer to produce a substantially flat steam temperature curve.

Water is normally supplied to the upper drum by any suitable means. A pair of solid water downcomers 74 are provided in the front and rear walls of the housing to carry the water from the upper drum to the lower drums. These downcomers may be located either on the outer surface or in the outer areas of the walls so that they will not come in contact with any of the heat from the combustion products. With this arrangement a steady supply of steam free water is assured to the lower drums, and all of the water walls and convection water tubes will act as hot Water and steam risers. Since this is a natural circulation system, water should be supplied from both ends and from the center of the upper drum to prevent an unbalance in the water level of the upper drum.

A small group of tubes 76 positioned in the space between baflle 48 and wall 28 are used to convey steam free water from the center of the upper drum to the center of the lower drums. It can be seen that baffle 48 is located just beyond the chimney outlets so that these tubes are not in the normal flow path of the combustion products and are not heated to any great extent by the flow of com bustion products. Vent openings 78 are provided on the top and bottom of the baffle to allow for an even temperature around tubes 76 but the combustion products temperatures at this point will be too low to have any appreciable effect on the water in these tubes.

Steam generating units of this type can be used with any source of combustion products. Apertures 36 in the front wall can be adapted to support either liquid or gaseous fuel burners. The central portion of the floor of the furnace space can be removed as shown in dotted line at 80 in FIGS. 1 and 2 for admission of hot combustion products from any other source either as a primary or auxiliary supply. This design makes this unit readily adaptable to receive combustion products from other apparatus arranged below the primary furnace space or to receive waste goods from other combustion sources entering the primary furnace space through the bottom.

In operating the steam generator unit, combustion products are admitted to the primary furnace space within the confines of the water walls where primary combustion occurs. The primary furnace space extends the full width of the housing and is sufliciently deep to allow for substantially complete burning therein. The hot combustion products are then drawn into the secondary furnace space 42 between water walls 40. The flow of hot combustion products around the ends of Walls 28 will cause an eddy current or turbulent effect at the entrance to the secondary furnace space which aids in mixing the combustion products to complete the burning of any unburned material. The combustion products will flow toward the rear Wall and will split and turn through and flow along the convection tube spaces of the housing toward the vertical walls 28 and out through the chimney outlet 56.

All of the water wall tubes and convection water tubes exposed to the combustion products in the primary furnace space, secondary furnace space and convection tube spaces will act as water and steam risers. This eliminates the blocking effect of steam generated in the tubes which would have to act to carry water from the upper drum to the lower drums. The water supplied to the upper drum will flow down to the lower drums through external downcomers 74 and tubes 76, thereby producing an even distribution of water throughout the drums and then establishing a positive Water circulation at all loads.

Steam from the upper drum may then be used or circulated through the superheater centrally located on the inner surface of the rear wall. The superheater is made up of a number of parallel tube elements that extend longitudinally into the central flow path. Each tube element is made up of one or more tubes for greater 12 .63

transfer surface area and each tube element is staggered with respect to its adjacent tube element to allow for a free flow of combustion products between the elements. The location of the Superheater at this point will cause the combustion products to split and turn through at least 90 in the Superheater. The end of each superheater tube element facing the hot combustion gases is thus exposed to essentially the same gas temperature and the same rate of radiant heat absorption. Superheater tube metal temperatures are thus essentially alike for each tube and with proper proportioning of radiant surface to convection surface, the resultant steam temperature obtained presents a very flat temperature curve.

Although only one embodiment of the present invention is shown and described herein, it should be apparent that various changes and modifications can be made within the scope of the appended claims.

I claim:

1. A boiler assembly comprising a housing having floor, roof, front, rear and side walls defining a forward primary furnace space and a rear hot gas space,

a boiler structure including an upper drum disposed generally in the top center of the housing and extending from the front wall to the rear wall, and

a pair of lower drums generally parallel to and of the same length as the upper drum and disposed on opposite sides of the floor of the housing,

longitudinal wall means extending from the primary furnace space through the rear gas path and terminating short of said rear wall thereby defining,

a centrally disposed secondary furnace space, a. superheater space and a reverse flow convection tube space on both sides of said secondary furnace space and superheater space,

water Wall tube means connecting the lower drums with the upper drum and lining the forward primary furnace space and the secondary furnace space,

convection tube means in the convection tube space connecting the lower drums to the upper drum, and superheater means mounted in said superheater space and aligned generally with the longitudinal axis of said secondary furnace space, said superheater means including a plurality of tubes lying in planes parallel to the longitudinal axis of said secondary furnace space to provide a minimum of resistance to the flow of combustion products through said superheater space and into the reverse flow convection tube space,

baffle means in said convection tube space to deflect the hot combustion products alternately up and down as they pass through the convection tubes,

and an outlet in the side walls and roof of said housing at the end of said convection tube space.

2. A boiler assembly according to claim 1 wherein said superheater means includes an inlet header and an outlet header disposed in a parallel relation in said rear wall,

superheater tube means connected at right angles between said headers,

and said superheater tubes are connected at right angles between said headers.

3. A steam generating assembly comprising a housing having floor, front, roof, rear and side Walls defining a primary furnace space and a secondary hot gas space and a boiler structure including an upper drum disposed generally in the top center of the housing and extending from the front Wall to the rear Wall,

and a pair of lower drums generally parallel to and being approximately of the same length as the upper drums and disposed on opposite sides of the floor of the housing,

longitudinal Wall means extending from the primary furnace space through the secondary hot gas space and terminating short of said rear wall, thereby defining a centrally disposed secondary furnace space of reduced width and a reverse flow convection tube space on either side of said secondary furnace space,

water wall tube means connecting the lower 'drums with the upper drum and lining the primary furnace space and the secondary furnace space,

convection tube means in the convection tube space connecting the lower drums to the upper drum,

baflie means in said convection tube space to deflect the hot combustion products alternately up and down as they pass through the convection tubes and openings in said side walls for discharging said combustion products,

a pair of external downcomers in the front wall and the rear wall connecting the front of said upper drum with the front of the lower drum and the rear of said upper drum with the rear of said lower drums means for supplying Water to said upper drum whereby said downcomers provide a solid. water connection from the upper drum to the lower drum and all the water wall tube means and convection tube means function as hot water risers,

and a blocking bafile at the end of said reverse flow convection tube space to isolate a section of convection tubes at the end of each reverse flow space and centrally disposed with respect to said side walls to act as water downcomers from the center of said upper drums to the center of said lower drums.

4. A steam generating assembly comprising a housing having floor, roof, front, rear and side walls defining a primary furnace space and a secondary hot gas space,

a boiler structure including an upper drum disposed generally in the top center of the housing and extending from the front Wall to the rear wall,

and a pair of lower drums generally parallel to and of approximately the same length as the upper drum and disposed on opposite sides of the floor of the housing,

longitudinal wall means extending from the primary furnace space through the secondary hot gas space and terminating short of said rear wall thereby defining a centrally disposed secondary furnace space and a reverse flow convection tube space on both sides of the secondary furnace space,

water wall tube means connecting the lower drums with the upper drum and lining the primary furnace space and the secondary furnace space,

convection tube means in the convection tube space connecting the lower drums to the upper drum,

bafile means in said convection tube space to deflect the hot combustion products alternately up and down as they pass through the convection tubes,

openings in said side walls for discharging said combustion products,

transversely extending walls connected to said side walls at right angles in said primary furnace space and terminating at the end of said longitudinal walls, said side walls deflecting the combustion products from said primary furnace space into said secondary furnace space and creating areas of turbulence at the intersections of the transverse walls and the longitudinal walls to provide complete combustion of the combustion products as they enter the combustion products flow path.

5. A steam generating unit comprising a housing having floor, roof, front, rear and side walls,

means for dividing the housing into a primary furnace space and a secondary hot gas space,

a boiler assembly in said housing including an upper drum and a pair of lower drums extending the full length of the housing,

tube means lining the furnace space and dividing the hot gas space into a centrally disposed secondary furnace space and side connection tube spaces, convection tubes in said convection tube spaces,

7 t3 outlets at the end of said convection tube spaces, 7. A steam generating unit according to clain15 wherebaflie means for deflecting hot gases up and down in in the surface area of said superheater assembly exposed said convection tube spaces; whereby combustion to radiant heat from the combustion products in the seeproducts entering said primary furnace space are diondary furnace space is so related to the surface area of rected through said furnace space and into said sec- 5 Said superheater exposed to convection hfaat that a fiat ondary furnace Space and turned through 0 into steam temperature curve 1s produced for said superheater.

said convection tube Space I References Cited by the Examiner and a superheater assembly extending longitudinally into said secondary furnace space and located so that UNITED STATES PATENTS the hot gases turn through 90 to 180 in said super- 10 2,222,530 11/40 Davey 122--347 heater assembly, said superheater assembly includ- 8 /44 Keenan 122328 ing a plurality of superheater tubes which li in 2,416,462 WflcoXSOn 122-235 planes parallel ,to the longitudinal axis of said sec- 2,754,307 7/ 56 Smith 1 235 2,807,243 9/57 Rehm 122-473 ondary furnace space. I 6. A steam generating unit according to claim 5 Wherc- 15 3022'774 2/62 Hamllton et a1 122 478 in said superheater assembly includes a plurality of tube elements parallelly arranged and having a number of tubes PERCY PATRICK Pnmary Examiner in each element of substantially the same configuration. KENNETH SPRAGUE, Examiner- 

1. A BOILER ASSEMBLY COMPRISING A HOUSING HAVING FLOOR, ROOF, FRONT, REAR AND SIDE WALLS DEFINING A FORWARD PRIMARY FURNACE SPACE AND A REAR HOT GAS SPACE, A BOILER STRUCTURE INCLUDING AN UPPER DRUM DISPOSED GENERALLY IN THE TOP CENTER OF THE HOUSING AND EXTENDING FROM THE FRONT WALL TO THE REAR WALL, AND A PAIR OF LOWER DRUMS GENERALLY PARALLEL TO AND OF THE SAME LENGTH AS THE UPPER DRUM AND DISPOSED ON OPPOSITE SIDES OF THE FLOOR OF THE HOUSING, LONGITUDINAL WALLS MEANS EXTENDING FROM THE PRIMARY FURNACE SPACE THROUGH THE REARR GAS PATH AND TERMINATING SHORT OF SAID REAR WALL THEREBY DEFINING, A CENTRALLY DISPOSED SECONDARY FURNACE SPACE, A SUPERHEATER SPACE AND A REVERSE FLOW CONVECTION TUVE SPACE ON BOTH SIDES OF SAID SECONDARY FURNACE SPACE AND SUPERHEATER SPACE, WATER WALL TUBE MEANS CONNECTING THE LOWER DRUMS WITH THE UPPER DRUM AND LINING THE FORWARD PRIMARY FURNACE SPACE AND THE SECONDARY FURNACE SPACE, CONVECTION TUBE MEANS IN THE CONVECTION TUBE SPACE CONNECTING THE LOWER DRUMS TO THE UPPER DRUM, AND SUPERHEATER MEANS MOUNTED IN SAID SUPERHEATER SPACE AND ALIGNED GENERALLY WITH THE LONGITUDINAL AXIS OF SAID SECONDARY FURNACE SPACE, SAID SUPERHEATER MEANS INCLUDING A PLURALITY OF TUBES LYING IN PLANES PARALLEL TO THE LONGITUDINAL AXIS OF SAID SECONDARY FURNACE SPACE TO PROVIDE A MINIMUM OF RESISTANCE OF THE FLOW OF COMBUSTION PRODUCTS THROUGH SAID SUPERHEATER SPACE AND INTO THE REVERSE FLOW CONVECTION TUBE SPACE, BAFFLE MEANS IN SAID CONVECTION TUBE SPACE TO DEFLECT THE HOT COMBUSTION PRODUCTS ALTERNATELY UP AND DOWN AS THEY PASS THROUGH THE CONVECTION TUBES, AND AN OUTLET IN THE SIDE WALLS AND ROOF OF SAID HOUSING AT THE END OF SAID CONVECTION TUBE SPACE. 